U.S. patent application number 14/551221 was filed with the patent office on 2016-05-26 for utilizing remote storage for network formation in iot networks.
The applicant listed for this patent is Cisco Technology, Inc.. Invention is credited to Wei Hong, Jonathan Hui, Jean-Philippe Vasseur.
Application Number | 20160149805 14/551221 |
Document ID | / |
Family ID | 56011345 |
Filed Date | 2016-05-26 |
United States Patent
Application |
20160149805 |
Kind Code |
A1 |
Hui; Jonathan ; et
al. |
May 26, 2016 |
UTILIZING REMOTE STORAGE FOR NETWORK FORMATION IN IOT NETWORKS
Abstract
In one embodiment, a device that is protected against a power
outage event in a network receives metrics used by a first node in
the network to select a routing link to a second node in the
network. The device stores the metrics used by the first node to
select the routing link to the second node. The device selects a
set of one or more of the metrics to provide to the first node
during network formation after a power outage event in the network.
The device provides the selected set of one or more of the metrics
to the first node, wherein the first node uses the provided set to
reestablish connectivity to the network.
Inventors: |
Hui; Jonathan; (Belmont,
CA) ; Vasseur; Jean-Philippe; (Saint Martin d'Uriage,
FR) ; Hong; Wei; (Berkeley, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cisco Technology, Inc. |
San Jose |
CA |
US |
|
|
Family ID: |
56011345 |
Appl. No.: |
14/551221 |
Filed: |
November 24, 2014 |
Current U.S.
Class: |
370/389 |
Current CPC
Class: |
Y02D 70/34 20180101;
H04W 40/125 20130101; Y02D 30/70 20200801; H04L 45/28 20130101;
Y02D 70/144 20180101; Y02D 70/22 20180101; Y02D 70/142
20180101 |
International
Class: |
H04L 12/703 20060101
H04L012/703 |
Claims
1. A method, comprising: receiving, at a device that is protected
against a power outage event in a network, metrics used by a first
node in the network to select a routing link to a second node in
the network; storing, at the device, the metrics used by the first
node to select the routing link to the second node; selecting, by
the device, a set of one or more of the metrics to provide to the
first node during network formation after the power outage event in
the network; and providing, by the device, the selected set of one
or more of the metrics to the first node, wherein the first node
uses the provided set to reestablish connectivity to the
network.
2. The method as in claim 1, wherein the metrics used by the first
node to select the routing link to the second node comprise an
expected transmission count (ETX) associated with the second node
or an average of a metric associated with the routing link over a
period of time.
3. The method as in claim 1, wherein the set of one or more of the
metrics provided to the first node comprise data indicative of one
or more adjacent nodes of the first node, wherein the first node
uses the set to cause the one or more adjacent nodes to reestablish
routing links between the one or more adjacent nodes and the first
node.
4. The method as in claim 1, wherein the set of one or more of the
metrics provided to the first node is a subset of the metrics used
by the first node to select the routing link to the second
node.
5. The method as in claim 4, wherein the metrics used by the first
node to select the routing link to the second node are associated
with a plurality of neighboring nodes of the first node, and
wherein the subset of the metric provided by the device to the
first node are associated with only a subset of the plurality of
neighboring nodes of the first node.
6. The method as in claim 5, further comprising: receiving, at the
device, a request from the first node for metrics regarding one or
more additional neighboring nodes that were not in the subset of
the plurality of neighboring nodes; and providing, by the device,
the metrics regarding the one or more additional neighboring nodes
to the first node.
7. The method as in claim 1, further comprising: determining, by
the device, that a degree of variation in a particular metric
received from the first node over time exceeds a threshold amount;
and preventing, by the device, the particular metric from being
provided to the first node after the power outage event, in
response to determining that the degree of variation in the
particular metric exceeds the threshold amount.
8. The method as in claim 1, further comprising: providing, by the
device, a notification to the first node that indicates that the
device is protected against power outage events.
9. The method as in claim 1, wherein the first node does not have a
persistent memory operable to store the metrics used by the first
node to select the routing link to the second node.
10. A method comprising: determining, by a first node in a network,
metrics regarding one or more neighbor nodes of the first node and
used by the first node to select a routing link to one of the
neighbor nodes; providing, by the first node, the metrics to a
network device that is protected against a power outage event in
the network; requesting, by the first node, the metrics from the
network device, after the power outage event in the network;
receiving, at the first node, at least a portion of the metrics
from the network device; and reestablishing, by the first node, the
routing link based on the at least a portion of the metrics
received from the network device.
11. The method as in claim 10, wherein the metrics used by the
first node to select the routing link comprise an expected
transmission count (ETX) metric or an average of a metric
associated with the routing link over a period of time.
12. The method as in claim 10, wherein the metrics are provided to
the network device in response to receiving a notification from the
network device that the network device is protected against power
outage events, and wherein the first node does not have a
persistent memory operable to store the metrics.
13. The method as in claim 10, further comprising: receiving, at
the first node after the power outage event, data from the network
device that is indicative of one or more adjacent nodes of the
first node; and causing, by the first node, the one or more
adjacent nodes to reestablish routing links between the adjacent
nodes and the first node, in response to receiving the data from
the network device that is indicative of the one or more adjacent
nodes of the first node.
14. An apparatus, comprising: one or more network interfaces to
communicate with a network; a processor coupled to the network
interfaces and configured to execute a process; and a memory
configured to store the process executable by the processor, the
process when executed operable to: receive metrics used by a first
node in the network to select a routing link to a second node in
the network; store, in the memory, the metrics used by the first
node to select the routing link to the second node; select a set of
one or more of the metrics to provide to the first node during
network formation after a power outage event in the network; and
provide the selected set of one or more of the parameters to the
first node, wherein the first node uses the provided set to
reestablish connectivity to the network.
15. The apparatus as in claim 14, wherein the metrics used by the
first node to select the routing link to the second node comprise
an expected transmission count (ETX) metric associated with the
second node or an average of a metric associated with the routing
link over a period of time.
16. The apparatus as in claim 14, wherein the set of one or more of
the metrics provided to the first node comprise data indicative of
one or more adjacent nodes of the first node, wherein the one or
more adjacent nodes use the set to establish routing links to the
first node after the power outage event in the network.
17. The apparatus as in claim 14, wherein the set of one or more of
the metrics provided to the first node is a subset of the metrics
used by the first node to select the routing link to the second
node.
18. The apparatus as in claim 17, wherein the metrics used by the
first node to select the routing link to the second node are
associated with a plurality of neighboring nodes of the first node,
and wherein the subset of the metric provided by the device to the
first node are associated with only a subset of the plurality of
neighboring nodes of the first node.
19. The apparatus as in claim 18, wherein the process when executed
is further operable to: receive a request from the first node for
metrics regarding one or more additional neighboring nodes that
were not in the subset of the plurality of neighboring nodes; and
provide the metrics regarding the one or more additional
neighboring nodes to the first node.
20. The apparatus as in claim 14, wherein the process when executed
is further operable to: determine that a degree of variation in a
particular metric received from the first node over time exceeds a
threshold amount; and prevent the particular metric from being
provided to the first node after the power outage event, in
response to determining that the degree of variation in the
particular metric exceeds the threshold amount.
21. The apparatus as in claim 14, wherein the process when executed
is further operable to: provide a notification to the first node
that indicates that the apparatus is protected against power outage
events.
22. The apparatus as in claim 14, wherein the first node does not
have a persistent memory operable to store the metrics used by the
first node to select the routing link to the second node.
23. An apparatus, comprising: one or more network interfaces to
communicate with a network; a processor coupled to the one or more
network interfaces and configured to execute a process; and a
memory configured to store the process executable by the processor,
the process when executed operable to: determine metrics regarding
one or more neighbor nodes of the apparatus and used by the
apparatus to select a routing link to one of the neighbor nodes;
provide the metrics to a network device that is protected against a
power outage event in the network; request the metrics from the
network device, after a power outage event in the network; receive
at least a portion of the metrics from the network device; and
reestablish the routing link based on the at least a portion of the
metrics received from the network device.
24. The apparatus as in claim 23, wherein the metrics used by the
first node to select the routing link comprise an expected
transmission count (ETX) metric or an average of a metric
associated with the routing link over a period of time.
25. The apparatus as in claim 23, wherein the metrics are provided
to the network device in response to receiving a notification from
the network device that the network device is protected against
power outage events, and wherein the first node does not have a
persistent memory operable to store the metrics.
26. The apparatus as in claim 23, wherein the process when executed
is further operable to: receive, after the power outage event, data
from the network device that is indicative of one or more adjacent
nodes of the apparatus; and cause the one or more adjacent nodes to
reestablish routing links between the adjacent nodes and the
apparatus, in response to receiving the data from the network
device that is indicative of the one or more adjacent nodes of the
apparatus.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to computer
networks, and, more particularly, to utilizing remote storage for
network formation in Internet of Things (IoT) networks.
BACKGROUND
[0002] Low Power and Lossy Networks (LLNs), e.g., sensor networks,
have a myriad of applications, such as Smart Grid and Smart Cities.
Various challenges are presented with LLNs, such as lossy links,
low bandwidth, low memory and/or processing capability of a device,
etc. Changing environmental conditions may also affect device
communications. For example, physical obstructions (e.g., changes
in the foliage density of nearby trees, the opening and closing of
doors, etc.), changes in interference (e.g., from other wireless
networks or devices), propagation characteristics of the media
(e.g., temperature or humidity changes, etc.), and the like, also
present unique challenges to LLNs.
[0003] In contrast to many traditional computer networks, LLN
devices typically communicate via shared-media links. For example,
LLN devices that communicate wirelessly may communicate using
overlapping wireless channels (e.g., frequencies). In other cases,
LLN devices may communicate with one another using shared power
line communication (PLC) links. For example, in a Smart Grid
deployment, an electric utility may distribute power to various
physical locations. At each location may be a smart meter that
communicates wirelessly and/or using the electrical power
distribution line itself as a communication medium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The embodiments herein may be better understood by referring
to the following description in conjunction with the accompanying
drawings in which like reference numerals indicate identically or
functionally similar elements, of which:
[0005] FIG. 1 illustrates an example communication network;
[0006] FIG. 2 illustrates an example network device/node;
[0007] FIG. 3 illustrates an example routing protocol message
format;
[0008] FIG. 4 illustrates an example directed acyclic graph (DAG)
in the network;
[0009] FIGS. 5A-5C illustrate an example of the remote storage of
network metrics;
[0010] FIGS. 6A-6D illustrate an example of network (re)formation
after a power outage event;
[0011] FIGS. 7A-7C illustrate an example of child node information
being provided to a network node;
[0012] FIG. 8 illustrates an example simplified procedure for
facilitating network re(formation) after a power outage event;
[0013] FIG. 9 illustrates an example simplified procedure for
providing additional metrics to a network node; and
[0014] FIG. 10 illustrates an example simplified procedure for
storing network metrics on a remote device.
DESCRIPTION OF EXAMPLE EMBODIMENTS
Overview
[0015] According to one or more embodiments of the disclosure, a
device that is protected against a power outage event in a network
receives metrics used by a first node in the network to select a
routing link to a second node in the network. The device stores the
metrics used by the first node to select the routing link to the
second node. The device selects a set of one or more of the metrics
to provide to the first node during network formation after the
power outage event in the network. The device provides the selected
set of one or more of the metrics to the first node, wherein the
first node uses the provided set to reestablish connectivity to the
network.
[0016] In further embodiments, a first node in a network determines
metrics regarding one or more neighbor nodes of the first node and
are used by the first node to select a routing link to one of the
neighbor nodes. The first node provides the metrics to a network
device that is protected against a power outage event in the
network. The first node requests the metrics from the network
device, after the power outage event in the network. The first node
receives at least a portion of the metrics from the network device.
The first node reestablishes the routing link based on the at least
a portion of the metrics received from the network device.
DESCRIPTION
[0017] A computer network is a geographically distributed
collection of nodes interconnected by communication links and
segments for transporting data between end nodes, such as personal
computers and workstations, or other devices, such as sensors, etc.
Many types of networks are available, ranging from local area
networks (LANs) to wide area networks (WANs). LANs typically
connect the nodes over dedicated private communications links
located in the same general physical location, such as a building
or campus. WANs, on the other hand, typically connect
geographically dispersed nodes over long-distance communications
links, such as common carrier telephone lines, optical lightpaths,
synchronous optical networks (SONET), synchronous digital hierarchy
(SDH) links, or Powerline Communications (PLC) such as IEEE 61334,
IEEE 1901.2, and others. In addition, a Mobile Ad-Hoc Network
(MANET) is a kind of wireless ad-hoc network, which is generally
considered a self-configuring network of mobile routers (and
associated hosts) connected by wireless links, the union of which
forms an arbitrary topology.
[0018] Smart object networks, such as sensor networks, in
particular, are a specific type of network having spatially
distributed autonomous devices such as sensors, actuators, etc.,
that cooperatively monitor physical or environmental conditions at
different locations, such as, e.g., energy/power consumption,
resource consumption (e.g., water/gas/etc. for advanced metering
infrastructure or "AMI" applications) temperature, pressure,
vibration, sound, radiation, motion, pollutants, etc. Other types
of smart objects include actuators, e.g., responsible for turning
on/off an engine or perform any other actions. Sensor networks, a
type of smart object network, are typically shared-media networks,
such as wireless or PLC networks. That is, in addition to one or
more sensors, each sensor device (node) in a sensor network may
generally be equipped with a radio transceiver or other
communication port such as PLC, a microcontroller, and an energy
source, such as a battery. Often, smart object networks are
considered field area networks (FANs), neighborhood area networks
(NANs), etc. Generally, size and cost constraints on smart object
nodes (e.g., sensors) result in corresponding constraints on
resources such as energy, memory, computational speed and
bandwidth.
[0019] FIG. 1 is a schematic block diagram of an example computer
network 100 illustratively comprising nodes/devices 200 (e.g.,
labeled as shown, "root," "11," "12," . . . "45," and described in
FIG. 2 below) interconnected by various methods of communication.
For instance, the links 105 may be wired links or shared media
(e.g., wireless links, PLC links, etc.) where certain nodes 200,
such as, e.g., routers, sensors, computers, etc., may be in
communication with other nodes 200, e.g., based on distance, signal
strength, current operational status, location, etc. Those skilled
in the art will understand that any number of nodes, devices,
links, etc. may be used in the computer network, and that the view
shown herein is for simplicity. Also, those skilled in the art will
further understand that while the network is shown in a certain
orientation, particularly with a "root" node, the network 100 is
merely an example illustration that is not meant to limit the
disclosure.
[0020] Data packets 140 (e.g., traffic and/or messages sent between
the devices/nodes) may be exchanged among the nodes/devices of the
computer network 100 using predefined network communication
protocols such as certain known wired protocols, wireless protocols
(e.g., IEEE Std. 802.15.4, WiFi, Bluetooth.RTM., etc.), PLC
protocols, or other shared-media protocols where appropriate. In
this context, a protocol consists of a set of rules defining how
the nodes interact with each other.
[0021] FIG. 2 is a schematic block diagram of an example
node/device 200 that may be used with one or more embodiments
described herein, e.g., as any of the nodes shown in FIG. 1 above.
The device may comprise one or more network interfaces 210 (e.g.,
wired, wireless, PLC, etc.), at least one processor 220, and a
memory 240 interconnected by a system bus 250, as well as a power
supply 260 (e.g., battery, plug-in, etc.). In some embodiments,
power supply 260 may be a single power supply. In other
embodiments, however, power supply 260 may include a primary power
supply (e.g., a power supply from a power line) and a backup power
supply such as, but not limited to, a battery or other charge
storage device (e.g., an ultra-capacitor, etc.), a solar panel, or
any other power supply configured to continue powering device 200
when the primary power supply is unavailable (e.g., during a power
outage event).
[0022] The network interface(s) 210 include the mechanical,
electrical, and signaling circuitry for communicating data over
links 105 coupled to the network 100. The network interfaces may be
configured to transmit and/or receive data using a variety of
different communication protocols. Note, further, that the nodes
may have two different types of network connections 210, e.g.,
wireless and wired/physical connections, and that the view herein
is merely for illustration. Also, while the network interface 210
is shown separately from power supply 260, for PLC the network
interface 210 may communicate through the power supply 260, or may
be an integral component of the power supply. In some specific
configurations the PLC signal may be coupled to the power line
feeding into the power supply.
[0023] The memory 240 comprises a plurality of storage locations
that are addressable by the processor 220 and the network
interfaces 210 for storing software programs and data structures
associated with the embodiments described herein. Note that certain
devices may have limited memory or no memory (e.g., no memory for
storage other than for programs/processes operating on the device
and associated caches). The processor 220 may comprise hardware
elements or hardware logic adapted to execute the software programs
and manipulate the data structures 245. An operating system 242,
portions of which are typically resident in memory 240 and executed
by the processor, functionally organizes the device by, inter alia,
invoking operations in support of software processes and/or
services executing on the device. These software processes and/or
services may comprise routing process/services 244 and an
illustrative network formation process 248, as described herein.
Note that while network formation process 248 is shown in
centralized memory 240, alternative embodiments provide for the
process to be specifically operated within the network interfaces
210, such as a component of a MAC layer (process "248a").
[0024] It will be apparent to those skilled in the art that other
processor and memory types, including various computer-readable
media, may be used to store and execute program instructions
pertaining to the techniques described herein. Also, while the
description illustrates various processes, it is expressly
contemplated that various processes may be embodied as modules
configured to operate in accordance with the techniques herein
(e.g., according to the functionality of a similar process).
Further, while the processes have been shown separately, those
skilled in the art will appreciate that processes may be routines
or modules within other processes.
[0025] Routing process (services) 244 includes computer executable
instructions executed by the processor 220 to perform functions
provided by one or more routing protocols, such as proactive or
reactive routing protocols as will be understood by those skilled
in the art. These functions may, on capable devices, be configured
to manage a routing/forwarding table (a data structure 245)
including, e.g., data used to make routing/forwarding decisions. In
particular, in proactive routing, connectivity is discovered and
known prior to computing routes to any destination in the network,
e.g., link state routing such as Open Shortest Path First (OSPF),
or Intermediate-System-to-Intermediate-System (ISIS), or Optimized
Link State Routing (OLSR). Reactive routing, on the other hand,
discovers neighbors (i.e., does not have an a priori knowledge of
network topology), and in response to a needed route to a
destination, sends a route request into the network to determine
which neighboring node may be used to reach the desired
destination. Example reactive routing protocols may comprise Ad-hoc
On-demand Distance Vector (AODV), Dynamic Source Routing (DSR),
DYnamic MANET On-demand Routing (DYMO), etc. Notably, on devices
not capable or configured to store routing entries, routing process
244 may consist solely of providing mechanisms necessary for source
routing techniques. That is, for source routing, other devices in
the network can tell the less capable devices exactly where to send
the packets, and the less capable devices simply forward the
packets as directed.
[0026] Low power and Lossy Networks (LLNs), e.g., certain sensor
networks, may be used in a myriad of applications such as for
"Smart Grid" and "Smart Cities." A number of challenges in LLNs
have been presented, such as:
[0027] 1) Links are generally lossy, such that a Packet Delivery
Rate/Ratio (PDR) can dramatically vary due to various sources of
interferences, e.g., considerably affecting the bit error rate
(BER);
[0028] 2) Links are generally low bandwidth, such that control
plane traffic must generally be bounded and negligible compared to
the low rate data traffic;
[0029] 3) There are a number of use cases that require specifying a
set of link and node metrics, some of them being dynamic, thus
requiring specific smoothing functions to avoid routing
instability, considerably draining bandwidth and energy;
[0030] 4) Constraint-routing may be required by some applications,
e.g., to establish routing paths that will avoid non-encrypted
links, nodes running low on energy, etc.;
[0031] 5) Scale of the networks may become very large, e.g., on the
order of several thousands to millions of nodes; and
[0032] 6) Nodes may be constrained with a low memory, a reduced
processing capability, a single power supply, etc.
[0033] In other words, LLNs are a class of network in which both
the routers and their interconnect are constrained: LLN routers
typically operate with constraints, e.g., processing power, memory,
and/or energy, and their interconnects are characterized by,
illustratively, high loss rates, low data rates, and/or
instability. LLNs are comprised of anything from a few dozen and up
to thousands or even millions of LLN routers, and support
point-to-point traffic (between devices inside the LLN),
point-to-multipoint traffic (from a central control point to a
subset of devices inside the LLN) and multipoint-to-point traffic
(from devices inside the LLN towards a central control point).
[0034] An example implementation of LLNs is an "Internet of Things"
network. Loosely, the term "Internet of Things" or "IoT" may be
used by those in the art to refer to uniquely identifiable objects
(things) and their virtual representations in a network-based
architecture. In particular, the next frontier in the evolution of
the Internet is the ability to connect more than just computers and
communications devices, but rather the ability to connect "objects"
in general, such as lights, appliances, vehicles, HVAC (heating,
ventilating, and air-conditioning), windows and window shades and
blinds, doors, locks, etc. The "Internet of Things" thus generally
refers to the interconnection of objects (e.g., smart objects),
such as sensors and actuators, over a computer network (e.g., IP),
which may be the Public Internet or a private network. Such devices
have been used in the industry for decades, usually in the form of
non-IP or proprietary protocols that are connected to IP networks
by way of protocol translation gateways. With the emergence of a
myriad of applications, such as the smart grid, smart cities, and
building and industrial automation, and cars (e.g., that can
interconnect millions of objects for sensing things like power
quality, tire pressure, and temperature and that can actuate
engines and lights), it has been of the utmost importance to extend
the IP protocol suite for these networks.
[0035] An example protocol specified in an Internet Engineering
Task Force (IETF) Proposed Standard, Request for Comment (RFC)
6550, entitled "RPL: IPv6 Routing Protocol for Low Power and Lossy
Networks" by Winter, et al. (March 2012), provides a mechanism that
supports multipoint-to-point (MP2P) traffic from devices inside the
LLN towards a central control point (e.g., LLN Border Routers
(LBRs) or "root nodes/devices" generally), as well as
point-to-multipoint (P2MP) traffic from the central control point
to the devices inside the LLN (and also point-to-point, or "P2P"
traffic). RPL (pronounced "ripple") may generally be described as a
distance vector routing protocol that builds a Directed Acyclic
Graph (DAG) for use in routing traffic/packets 140, in addition to
defining a set of features to bound the control traffic, support
repair, etc. Notably, as may be appreciated by those skilled in the
art, RPL also supports the concept of Multi-Topology-Routing (MTR),
whereby multiple DAGs can be built to carry traffic according to
individual requirements.
[0036] A DAG is a directed graph having the property that all edges
(and/or vertices) are oriented in such a way that no cycles (loops)
are supposed to exist. All edges are included in paths oriented
toward and terminating at one or more root nodes (e.g.,
"clusterheads or "sinks"), often to interconnect the devices of the
DAG with a larger infrastructure, such as the Internet, a wide area
network, or other domain. In addition, a Destination Oriented DAG
(DODAG) is a DAG rooted at a single destination, i.e., at a single
DAG root with no outgoing edges. A "parent" of a particular node
within a DAG is an immediate successor of the particular node on a
path towards the DAG root, such that the parent has a lower "rank"
than the particular node itself, where the rank of a node
identifies the node's position with respect to a DAG root (e.g.,
the farther away a node is from a root, the higher is the rank of
that node). Further, in certain embodiments, a sibling of a node
within a DAG may be defined as any neighboring node which is
located at the same rank within a DAG. Note that siblings do not
necessarily share a common parent, and routes between siblings are
generally not part of a DAG since there is no forward progress
(their rank is the same). Note also that a tree is a kind of DAG,
where each device/node in the DAG generally has one parent or one
preferred parent.
[0037] DAGs may generally be built (e.g., by routing process 244)
based on an Objective Function (OF). The role of the Objective
Function is generally to specify rules on how to build the DAG
(e.g. number of parents, backup parents, etc.).
[0038] In addition, one or more metrics/constraints may be
advertised by the routing protocol to optimize the DAG against.
Also, the routing protocol allows for including an optional set of
constraints to compute a constrained path, such as if a link or a
node does not satisfy a required constraint, it is "pruned" from
the candidate list when computing the best path. (Alternatively,
the constraints and metrics may be separated from the OF.)
Additionally, the routing protocol may include a "goal" that
defines a host or set of hosts, such as a host serving as a data
collection point, or a gateway providing connectivity to an
external infrastructure, where a DAG's primary objective is to have
the devices within the DAG be able to reach the goal. In the case
where a node is unable to comply with an objective function or does
not understand or support the advertised metric, it may be
configured to join a DAG as a leaf node. As used herein, the
various metrics, constraints, policies, etc., are considered "DAG
parameters."
[0039] Illustratively, example metrics used to select paths (e.g.,
preferred parents) may comprise cost, delay, latency, bandwidth,
expected transmission count (ETX), etc., while example constraints
that may be placed on the route selection may comprise various
reliability thresholds, restrictions on battery operation,
multipath diversity, bandwidth requirements, transmission types
(e.g., wired, wireless, etc.). The OF may provide rules defining
the load balancing requirements, such as a number of selected
parents (e.g., single parent trees or multi-parent DAGs). Notably,
an example for how routing metrics and constraints may be obtained
may be found in an IETF RFC, entitled "Routing Metrics used for
Path Calculation in Low Power and Lossy Networks"<RFC 6551>
by Vasseur, et al. (March 2012 version). Further, an example OF
(e.g., a default OF) may be found in an IETF RFC, entitled "RPL
Objective Function 0"<RFC 6552> by Thubert (March 2012
version) and "The Minimum Rank Objective Function with Hysteresis"
<RFC 6719> by O. Gnawali et al. (September 2012 version).
[0040] Building a DAG may utilize a discovery mechanism to build a
logical representation of the network, and route dissemination to
establish state within the network so that routers know how to
forward packets toward their ultimate destination. Note that a
"router" refers to a device that can forward as well as generate
traffic, while a "host" refers to a device that can generate but
does not forward traffic. Also, a "leaf" may be used to generally
describe a non-router that is connected to a DAG by one or more
routers, but cannot itself forward traffic received on the DAG to
another router on the DAG. Control messages may be transmitted
among the devices within the network for discovery and route
dissemination when building a DAG.
[0041] According to the illustrative RPL protocol, a DODAG
Information Object (DIO) is a type of DAG discovery message that
carries information that allows a node to discover a RPL Instance,
learn its configuration parameters, select a DODAG parent set, and
maintain the upward routing topology. In addition, a Destination
Advertisement Object (DAO) is a type of DAG discovery reply message
that conveys destination information upwards along the DODAG so
that a DODAG root (and other intermediate nodes) can provision
downward routes. A DAO message includes prefix information to
identify destinations, a capability to record routes in support of
source routing, and information to determine the freshness of a
particular advertisement. Notably, "upward" or "up" paths are
routes that lead in the direction from leaf nodes towards DAG
roots, e.g., following the orientation of the edges within the DAG.
Conversely, "downward" or "down" paths are routes that lead in the
direction from DAG roots towards leaf nodes, e.g., generally going
in the opposite direction to the upward messages within the
DAG.
[0042] Generally, a DAG discovery request (e.g., DIO) message is
transmitted from the root device(s) of the DAG downward toward the
leaves, informing each successive receiving device how to reach the
root device (that is, from where the request is received is
generally the direction of the root). Accordingly, a DAG is created
in the upward direction toward the root device. The DAG discovery
reply (e.g., DAO) may then be returned from the leaves to the root
device(s) (unless unnecessary, such as for UP flows only),
informing each successive receiving device in the other direction
how to reach the leaves for downward routes. Nodes that are capable
of maintaining routing state may aggregate routes from DAO messages
that they receive before transmitting a DAO message. Nodes that are
not capable of maintaining routing state, however, may attach a
next-hop parent address. The DAO message is then sent directly to
the DODAG root that can in turn build the topology and locally
compute downward routes to all nodes in the DODAG. Such nodes are
then reachable using source routing techniques over regions of the
DAG that are incapable of storing downward routing state. In
addition, RPL also specifies a message called the DIS (DODAG
Information Solicitation) message that is sent under specific
circumstances so as to discover DAG neighbors and join a DAG or
restore connectivity.
[0043] FIG. 3 illustrates an example simplified control message
format 300 that may be used for discovery and route dissemination
when building a DAG, e.g., as a DIO, DAO, or DIS message. Message
300 illustratively comprises a header 310 with one or more fields
312 that identify the type of message (e.g., a RPL control
message), and a specific code indicating the specific type of
message, e.g., a DIO, DAO, or DIS. Within the body/payload 320 of
the message may be a plurality of fields used to relay the
pertinent information. In particular, the fields may comprise
various flags/bits 321, a sequence number 322, a rank value 323, an
instance ID 324, a DODAG ID 325, and other fields, each as may be
appreciated in more detail by those skilled in the art. Further,
for DAO messages, additional fields for destination prefixes 326
and a transit information field 327 may also be included, among
others (e.g., DAO_Sequence used for ACKs, etc.). For any type of
message 300, one or more additional sub-option fields 328 may be
used to supply additional or custom information within the message
300. For instance, an objective code point (OCP) sub-option field
may be used within a DIO to carry codes specifying a particular
objective function (OF) to be used for building the associated DAG.
Alternatively, sub-option fields 328 may be used to carry other
certain information within a message 300, such as indications,
requests, capabilities, lists, notifications, etc., as may be
described herein, e.g., in one or more type-length-value (TLV)
fields.
[0044] FIG. 4 illustrates an example simplified DAG that may be
created, e.g., through the techniques described above, within
network 100 of FIG. 1. For instance, certain links 105 may be
selected for each node to communicate with a particular parent (and
thus, in the reverse, to communicate with a child, if one exists).
These selected links form the DAG 410 (shown as bolded lines),
which extends from the root node toward one or more leaf nodes
(nodes without children). Traffic/packets 140 (shown in FIG. 1) may
then traverse the DAG 410 in either the upward direction toward the
root or downward toward the leaf nodes, particularly as described
herein.
[0045] In certain IoT applications (e.g., Smart Grid AMI, etc.),
network operations may require supporting notifications regarding
power outages and power restorations. At a minimum, devices in a
mesh network may be configured to support Power Outage Notification
(PON) and Power Restoration Notification (PRN) messages. PONs allow
a utility to determine the occurrence and location of power
outages. Similarly, PRNs allow a utility to determine when and
where power is restored. PRNs following PONs may be used by the
utility to determine the duration of a power outage event (e.g.,
whether the power outage is momentary, temporary, or sustained).
PRNs may also be used to prevent unnecessary "truck rolls" (e.g.,
deployments of service technicians) that may be triggered by PONs.
PRNs may also provide real-time feedback when working to restore
power in the field.
[0046] Network (re)formation after PRNs are generated may present a
number of logistical challenges, due to the typically limited
capabilities of LLN devices. For example, full network
(re)formation may be time-intensive, as potentially hundreds of
devices are forced to rediscover neighbor devices and to reselect
routing paths. To speed up network (re)formation after a power
outage event, some techniques sacrifice making optimal routing
decisions in favor of establishing some baseline level of network
functionality. In such techniques, network (re)formation is often
based on partial information regarding the network, thereby leading
to suboptimal routing decisions. The network may then be adjusted
at a later time or over the course of time, to optimize routing in
the network.
[0047] In one example of a potential tradeoff between network
formation times and network optimization, a device may establish a
routing link with a neighboring device based on a single received
signal strength indication (RSSI)/link quality indication (LQI)
reading for the link, after power is restored. Since only a single
sample is needed to quantify the quality of the link, the device
may quickly rejoin the network. However, over the course of time,
the device may shift to using a more reliable link quality metric
and, if needed, readjust its routing strategy. For example, the
device may calculate an ETX metric for the link based on multiple
samples, to optimize its routing decisions at a later time.
[0048] In another example of a quick (re)formation technique, a
device may choose to route traffic to the first device that it
discovers and establish a default route to the discovered device.
Such an approach may be used in networks where sub-optimal routing
is acceptable until the network re-converges to a more optimal
state. However, in other cases, such as when critical applications
are supported by the network, the selection and use of sub-optimal
routes may be a limiting factor.
[0049] As noted above, LLN devices may be limited in terms of their
capabilities and resources. For example, many LLN devices may have
limited persistent storage capabilities, in contrast to traditional
computing devices. Thus, metrics that may be used by the LLN
devices to make optimal routing decisions may be lost during a
power outage event. Consequently, routing decisions after a power
outage are often made based on incomplete information regarding the
network, to return functionality to the network as soon as
possible.
[0050] Utilizing Remote Storage for Network Formation in IoT
Networks
[0051] The techniques herein provide mechanisms for using remote
storage and information on network devices that are protected
against a power outage event (e.g., devices that have backup power
sources and/or have sufficient persistent memory to store the
information during a power outage), to speed up the formation of a
more optimal routing topology after power is restored to the nodes.
In one aspect, network nodes may periodically report network
topology information to a protected device that is costly to
discover, evaluate, and/or compute (e.g., neighboring nodes, link
quality estimates, routes, etc.). In another aspect, child node
information may be obtained during network formation and advertised
to the child nodes, so that the child nodes can quickly connect to
their optimal parent(s). In yet another aspect, a protected device
may promulgate stored link quality estimates, to initialize the
link metrics at the nodes thereby avoiding the nodes from making
costly link quality estimates after power is restored. In a further
aspect, a protected device may select only a subset of link metrics
to promulgate when rebuilding the DAG topology (e.g., by selecting
only the most stable links in the network).
[0052] Specifically, according to one or more embodiments of the
disclosure as described in detail below, a device that is protected
against a power outage event in a network receives metrics used by
a first node in the network to select a routing link to a second
node in the network. The device stores the metrics used by the
first node to select the routing link to the second node. The
device selects a set of one or more of the metrics to provide to
the first node during network formation after a power outage event
in the network. The device provides the selected set of one or more
of the metrics to the first node, wherein the first node uses the
provided set to reestablish connectivity to the network.
[0053] Illustratively, the techniques described herein may be
performed by hardware, software, and/or firmware, such as in
accordance with the network formation process 248/248a, which may
include computer executable instructions executed by the processor
220 (or independent processor of interfaces 210) to perform
functions relating to the techniques described herein, e.g., in
conjunction with routing process 244. For example, the techniques
herein may be treated as extensions to conventional protocols, such
as the various PLC protocols or wireless communication protocols,
and as such, may be processed by similar components understood in
the art that execute those protocols, accordingly.
[0054] Operationally, a subset of the devices in a network may be
protected against power outages while other devices are not. For
example, some devices may be equipped with both primary and backup
power sources, while other nodes/devices may only have a primary
power source. In one implementation, a power-protected root
node/field area router (FAR) may be configured with a battery
backup system that provides hours of continued operation after the
primary power source becomes unavailable. Alternatively, or in
addition to, a device that is protected against power outages may
include persistent memory with enough free space to store
information about the network during a power outage event. In
various embodiments, a protected device may receive, store, and
provide any information on behalf of the non-protected nodes that
is useful for maintaining the network topology (e.g., after a power
outage event). Doing so may help speed up network (re)formation and
help the routing topology converge to an optimal solution more
quickly.
[0055] Referring now to FIGS. 5A-5C, an example of the remote
storage of network metrics is illustrated, according to various
embodiments. In some aspects, a network node that does not have a
backup power supply may provide any network information to a
power-protected, remote device that is costly to discover,
evaluate, and/or compute. For example, as shown in FIG. 5A, node 34
may provide information 502 to the Root/FAR (e.g., a
power-protected device) that was used to make routing decisions
regarding node 34. For example, information 502 may include
identifiers for any discovered neighbors of node 34 (e.g., node 33,
etc.), link quality metrics associated with the neighbors of node
34 (e.g., an ETX metric, etc.), routing information (e.g.,
information regarding the parent(s) and/or children of node 34 in
DAG 410), and/or any other information that may be used to select a
routing link between node 34 and a neighboring node.
[0056] As would be appreciated, replicating the data in information
502 may be time and resource consuming, after power is restored to
the network. In one example, discovering neighbors in a dense
environment may take a significant amount of time primarily due to
shared-media contention. To avoid contention, some techniques may
have the nodes/devices broadcast their presences asynchronously.
Notably, however, neighbor discovery would be much more efficient
if a device could announce its presence without having to arbitrate
access to the media. In another example, as noted above, evaluating
link qualities also requires significant time and resource
overhead. For example, evaluating ETX metrics properly requires
exchanging a number of packets over time with each neighboring
device. In yet another example, selecting and evaluating routes can
take significant time to allow for routing information to
propagate. Furthermore, multiple phases may be required to allow
the routes to be optimized. Other examples of metrics that are not
easily obtained include those that are based on one or more
statistics. For example, other metrics may include an average RSSI
or an average signal to noise ratio (SNR) over the course of a
certain time period.
[0057] Node 34 may not have persistent storage enough to store
information 502 locally, for various reasons. First, persistent
storage is relatively expensive and, consequently, many existing
LLN devices in IoT networks have either limited persistent storage
or, alternatively, no free persistent storage at all. Second,
writing information 502 to flash memory may be energy intensive,
which may not be desirable for certain applications (e.g., in
devices that are expected to last at least twenty years in the
field). Third, flash technologies typically have a limited number
of writes that may be used before device failure, which may prove
problematic when storing information that may be constantly
changing (e.g., information regarding the changing conditions of
the network).
[0058] In various embodiments, node 34 may provide information 502
to the FAR/Root device in conjunction with the routing protocol
used within network 100. For example, if network 100 uses RPL in
non-storing mode, much of information 502 may already be provided
to the FAR/Root. In another example, network nodes may already be
sending periodic updates about the network topology to the FAR/Root
(e.g., as part of RPL DAO messages). In other embodiments, some or
all of information 502 may be sent to the FAR/Root device as a
message that is independent of the routing protocol.
[0059] While the FAR/Root node is shown as receiving information
502 from node 34, information 502 may alternatively be provided to
any power-protected device in network 100 (e.g., other nodes,
etc.). In various embodiments, a power-protected device may
advertise its storage capabilities to other nodes/devices in
network 100. For example, each power-protected device may advertise
its storage capability to other devices in the field and/or to the
FAR/Root using a routing extension (e.g., in accordance with
RFC6551) that indicates the amount of memory available on the
protected device for storage of information 502.
[0060] In response to receiving network information 502 from node
34, the FAR/Root or other power-protected device may store
information 502 locally, as shown in FIG. 5B. In some embodiments,
the power-protected device may be operable to dynamically determine
which data in information 502 is stored, how often information 502
is reported or stored, and/or where information 502 is stored. For
example, as shown in FIG. 5C, the FAR/Root node may select which
metrics or other network information received from node 34 should
be provided back to node 34 after a power outage event.
[0061] In one embodiment, a power-protected device may model the
variation of a particular performance metric over time and is
received for storage. For example, the FAR/Root node shown or
another power-protected device storing network information 502 may
use metrics received over the course of time to model the amount of
variation in the metrics (e.g., using a time-series approach such
as an autoregressive-moving-average model, using a learning machine
model, etc.). In various embodiments, the power-protected device
may use the modeled variations in the performance metrics, to
select only links that the device deems stable. Notably, link
performance metrics should ideally exhibit minimal or no variation
at all. In some embodiments, if the power-protected device
determines that the amount of variation in a particular metric
exceeds a threshold amount, it may prevent the metric from being
provided back to the originating node. In doing so, the
power-protected device may control which routing links are to be
used by the node during network (re)formation. For example, the
power-protected device may prevent a highly variable metric from
being stored in its local memory or otherwise prevent the metric
from being sent back to the node. In some embodiments, the
threshold amount of variation in a performance metric that may be
acceptable may be based on a network policy. For example, a network
link that exhibits high volatility in its performance metrics may
be deemed too "risky" to use during network formation after a power
outage event. Such a threshold may also be based on the type of
traffic carried by the link, in one embodiment.
[0062] Referring now to FIGS. 6A-6D, an example of network
(re)formation after a power outage event is shown, according to
various embodiments. As shown in FIG. 6A, assume that a power
outage event is occurring, thereby preventing some or all of nodes
11-45 from functioning and/or communicating. In FIG. 6B, assume
that power has been restored, thereby allowing nodes 11-45 to begin
communicating again. In such a case, a power-protected device
(e.g., the FAR/Root node shown) may provide stored network
information 602 back to a network node (e.g., node 34) that may be
used by the node to reestablish its routing links. For example,
network information 602 may include initial link quality metrics
(e.g., ETX metrics). As mentioned previously, some link metrics
such as ETX metrics are both computationally expensive and time
consuming to calculate.
[0063] Information 602 may be provided to node 34 in a number of
different ways. In one embodiment, information 602 may be
piggybacked onto messages used by one or more existing protocol
messages sent as part of the network formation process (e.g., EAP,
DHCPv6, RPL, etc.). In another embodiment, information 602 may be
provided in a completely separate control protocol. Information 602
may also be provided to node 34 by the FAR/Root device in response
to the FAR/Root receiving a request from node 34 (e.g., after node
34 comes back online) or, alternatively, may be provided on a push
basis (e.g., after the FAR/Root determines that power has been
restored).
[0064] In various embodiments, the FAR/Root node or other
power-protected device may control what information is included in
information 602 provided to node 34. In one embodiment, information
602 may only include information regarding a single neighbor, link,
and/or route. For example, the FAR/Root device may purposely limit
the data in information 602 to information regarding the link
between node 34 and node 24. Such an option may be used, for
example, to provide only the minimal amount of information to a
node needed for the node to reattach to the network and begin
delivering messages. In another embodiment, the FAR/Root or other
protected device may provide all available information associated
with node 34 in information 602 or limit the amount of information
602 to an intermediary amount of data. For example, information 602
may be limited to including metrics regarding up to a specific
number of neighbors of a node (e.g., information regarding up to
three neighbors and routes, etc.).
[0065] In cases in which information 602 includes information
regarding only a subset of the neighbors of a given node,
additional information regarding any excluded neighbors may also be
provided to the node at a later time. For example, assume that the
FAR/Root initially only provides information regarding the
previously existing routing link between node 34 and 24 in
information 602, so that node 34 can reestablish its routing link
to node 24 (e.g., as part of a reformation of DAG 410), as shown in
FIG. 6C. As shown in FIG. 6D, node 34 may then later send a request
604 to the FAR/Root for information regarding any other links/nodes
that were previously excluded from information 602 (e.g.,
information regarding node 33, etc.). For example, node 34 may send
request 604 to the FAR/Root device, in response to a failure in the
link with node 24 or after the network stabilizes.
[0066] In various implementations, a power-protected device such as
a FAR/Root device may provide stored network information to the
nodes in the network, to reform the same routing topology that was
in use prior to the power outage event occurring. For example, as
shown in FIG. 6D, the FAR/Root device may prompt the reformation of
DAG 410 by providing information 602. In particular, the FAR/Root
device may reuse the existing routing topology information that it
has already stored, rather than waiting for route updates (e.g.,
RPL DAO messages) as nodes join the network, before forwarding
messages into the mesh. Using the same routing topology also
reduces the need for RPL DAO traffic, which may reduce network
formation time and control traffic overhead.
[0067] LLN nodes/devices may use the network information stored by
a protected device in a number of different ways. In some cases,
the power-protected device may provide a list of one or more child
nodes of a particular node, which may be advertised in a routing
protocol message. For example, as shown in FIG. 7A, the FAR/Root
device may provide child information 702 to node 34 as part of an
RPL DIO message (e.g., using a custom RPL option that includes an
explicit list of node identifiers, a Bloom filter, etc.).
Neighboring devices receiving the RPL DIO message and named in the
list can then quickly determine which neighbors to focus on as
parents. For example, assume that child information 702 indicates
that node 45 should be a child node of node 34 and/or include link
metrics regarding the link between node 45 and 34 (e.g., an ETX
metric) that may be used by node 45 to select node 34 as its
parent. In such a case, node 45 may use the received information to
determine that it should select node 34 as its DAG parent, as
illustrated in FIGS. 7B-7C. In cases in which the routing topology
is not a strict DAG, child information 702 may be sent to any
routing adjacencies (e.g., as opposed strictly child nodes).
[0068] As would be appreciated, changing RF conditions are a
defining characteristic of LLNs. However, many links may still be
characterized by long-term properties in implementations in which
the nodes are stationary (e.g., Smart Grid AMI deployments, etc.).
Typically, links that have lower link margins also exhibit greater
variations in their link metrics (e.g., success rates) over time.
Conversely, links that have higher link margins typically provide
greater success rates. According to the techniques herein, a
power-protected device may limit its storage of network information
to state information that may be helpful for quick network
formation, as opposed to information regarding the current routing
state of the network. For example, mesh routing protocols typically
attempt to choose paths that minimize latency by minimizing the
number of hops along a routing path. As a result, route metrics
often select links that have low link margin but provide good
reliability. In contrast, for purposes of network (re)formation,
power-protected device may store information regarding links that
have higher link margins, to help ensure that connectivity is
restored more quickly during network restoration. In other words,
the power-protected device is not limited to simply storing
information regarding the current routing topology, but may store
any network information that is useful for purposes of quickly
restoring connectivity to the network.
[0069] FIG. 8 illustrates an example simplified procedure for
facilitating network re(formation) after a power outage event, in
accordance with one or more embodiments described herein. The
procedure 800 may start at step 805, and continues to step 810,
where, as described in greater detail above, a network device
(e.g., device 200) receives information/metrics used by a first
network node to select a routing link to a second network node. In
various embodiments, the network device may be a power-protected
device that may continue its operation during a power outage event.
For example, a FAR may be equipped with a battery-backup system,
thereby allowing the FAR to continue functioning if its primary
power source is unavailable. In other embodiments, the device may
be protected against power outages by having free persistent memory
sufficient to store information across a power outage event. The
received information may include, for example, link metrics for the
link between the first and second nodes, link metrics for any links
between the first node and any of its other neighboring nodes,
identifiers for the neighboring nodes, or any other information
that may be used by the first node to select the link with the
second node as a routing link. Example metrics may include, but are
not limited to, ETX metrics or other performance metrics that may
require multiple samples to compute.
[0070] At step 815, the network device stores the received
information/metrics locally, as described in greater detail above.
In some cases, the device may store all of the information that it
receives regarding the state of the network. In other cases,
however, the network device may filter the received information,
prior to storage. For example, the network device may calculate one
or more statistics regarding a performance metric (e.g., an
average, etc.) and store the computed statistic, accordingly. In
some cases, the network device may also prevent the storage of
certain network information/metrics that it received. For example,
the network device may only store information regarding links that
it determines are sufficiently stable for purposes of network
(re)formation.
[0071] At step 820, as detailed above, the network device selects
which metrics are to be provided to the first node after a power
outage event occurs. In some cases, the network device may provide
only a subset of the total amount of network information associated
with the first node. For example, the network device may select
only information regarding a single neighbor of the first node,
regarding up to a fixed number of neighbors of the first node
(e.g., information regarding up to three neighbors), or regarding
all neighbors of the first node, to be provided back to the first
node. In various embodiments, the network device may select the
information to be provided to the first node based on the stability
of the selected link(s). For example, the network device may
prevent information regarding an unstable neighbor link from being
sent back to the first node, after a power outage event.
[0072] At step 825, the network device provides the
information/metric(s) selected in step 820 to the first node, as
described in greater detail above. In general, the provided
information/metric(s) may cause the first node to rejoin the
network in some manner. For example, the provided information may
cause the first node to reestablish its link to the second node as
its preferred routing link. In another example, the provided
information may cause the first node to establish a new routing
link with a different neighbor, if the network device determines
that doing so would provide a faster network formation time and/or
a more stable link to ensure connectivity. Procedure 800 then ends
at step 830.
[0073] FIG. 9 illustrates an example simplified procedure for
providing additional metrics to a network node, in accordance with
one or more embodiments described herein. The procedure 900 may
start at step 905, and continues to step 910, where, as described
in greater detail above, a network device (e.g., device 200) may
provide metrics to a node for only a subset of the node's
neighbors. For example, assume that a particular network node has
five neighbors within its transmission range. In such a case, the
network device may provide link metrics for only a single neighbor,
for purposes of (re)forming the network (e.g., after a power outage
event). In another example, the network device may provide metrics
for up to a fixed number of neighbors (e.g., three of the
neighbors). The selection of which neighbors' information is
provided to the particular node may be based on various factors
such as the degree of variability in the metrics, the overhead on
the network when providing the information to the node, or other
such factors.
[0074] At step 915, as described in greater detail above, the
network device may receive a request for additional neighbor
information/metrics from the node. For example, assume that the
network device provided only a minimal amount of information needed
for the node to rejoin the network after a power outage event. At a
later time, the node may request additional information that it may
use to make routing decisions. For example, if the node's routing
link loses connectivity or the network reformation process
stabilizes, the node may request additional information regarding
any of its other neighbors.
[0075] At step 920, the network device may provide the requested
metrics to the node, as highlighted above. For example, the network
device may provide the node with the complete set of information
associated with the node (e.g., information regarding all of the
node's neighbors). In another example, the network device may
provide another subset of the total information (e.g.,
information/metrics regarding the next preferred link) to the node.
In some embodiments, steps 910-920 may be repeated any number of
times in an iterative manner, thereby allowing the node to access
additional network information/metrics as needed. Procedure 900
then ends at step 925.
[0076] FIG. 10 illustrates an example simplified procedure for
storing network metrics on a remote device, in accordance with one
or more embodiments described herein. In general, procedure 1000
may be performed by an LLN node that is not protected against a
power outage event. The procedure 1000 may start at step 1005, and
continues to step 1010, where, as described in greater detail
above, the node may determine one or more metrics regarding any of
its neighboring nodes. For example, the node may determine an ETX
or other metric that quantifies the quality of the link between the
node and a given neighbor. In general, the metrics may be any
metric or metrics that the node may use to select a routing link
between itself and one of its neighboring device.
[0077] At step 1015, the node may provide the metrics to a
power-protected device, as detailed above. In particular, the
power-protected device may be any network device that is equipped
with a backup power source that allows the protected device to
continue operating during a power outage event. In general, LLN
devices typically do not have such backup systems and also
typically have limited persistent memory, meaning that the provided
metrics may otherwise be lost during a power outage event.
[0078] At step 1020, the node may request stored metrics from the
network device, after power is restored, as described in greater
detail above. For example, after power is restored to the node, the
node may request network information/metrics that cannot be
obtained quickly, such as an ETX link metric.
[0079] At step 1025, the node receives the requested metrics from
the network device, as detailed above. In various cases, the
received metrics may include the entirety of the metrics associated
with the node or only a subset of the complete dataset. For
example, the network device may select which metrics or other
information are to be provided back to the node, such that network
(re)formation occurs more quickly and/or the node takes advantage
of the most optimal route available to the node. In these cases,
the node may later request additional information/metrics, such as
when the selected routing link fails or the network is
stabilized.
[0080] At step 1030, the node uses the received metrics to
(re)establish a routing link in the network, as described in
greater detail above. For example, the node may rejoin the network
using a previously used link to a parent node based on the received
metrics from the protected network device. In doing so, the network
may be reformed in such a way that leverages information that would
otherwise be impractical to reproduce after a power outage event.
Procedure 1000 then ends at step 1035.
[0081] It should be noted that while certain steps within
procedures 800-1000 may be optional as described above, the steps
shown in FIGS. 8-10 are merely examples for illustration and
certain other steps may be included or excluded as desired.
Further, while a particular order of the steps is shown, this
ordering is merely illustrative, and any suitable arrangement of
the steps may be utilized without departing from the scope of the
embodiments herein. Moreover, while procedures 800-1000 are
described separately, certain steps from each procedure may be
incorporated into each other procedure, and the procedures are not
meant to be mutually exclusive.
[0082] The techniques described herein, therefore, provide
mechanisms for remotely storing network information on
power-protected devices, to help speed network formation.
Information such as neighbor identifies, link quality estimates
(e.g., ETX metrics, etc.), and routes typically require significant
time, energy, and channel utilization to recreate. By having this
information available during network formation, devices can more
quickly form a more optimal routing topology without basing routing
decisions on partial or unreliable information (e.g., using
RSSI/LQI metrics to estimate link quality, simply picking the node
that send the first RPL DIO message received by the node, etc.).
Further, by leveraging the existing routing topology stored on a
FAR/Root device, the FAR does not need to wait for route updates
(e.g., via RPL DAO messages) before delivering messages into the
mesh.
[0083] While there have been shown and described illustrative
embodiments that provide for the remote storage of network
information for purposes of network (re)formation, it is to be
understood that various other adaptations and modifications may be
made within the spirit and scope of the embodiments herein. For
example, certain embodiments have been shown and described herein
with relation to PLC networks. However, the embodiments in their
broader sense are not as limited, and may, in fact, be used with
other types of shared-media networks and/or protocols (e.g.,
wireless). In addition, while certain protocols are shown, such as
RPL, other suitable protocols may be used, accordingly.
[0084] The foregoing description has been directed to specific
embodiments. It will be apparent, however, that other variations
and modifications may be made to the described embodiments, with
the attainment of some or all of their advantages. For instance, it
is expressly contemplated that the components and/or elements
described herein can be implemented as software being stored on a
tangible (non-transitory) computer-readable medium (e.g.,
disks/CDs/RAM/EEPROM/etc.) having program instructions executing on
a computer, hardware, firmware, or a combination thereof.
Accordingly this description is to be taken only by way of example
and not to otherwise limit the scope of the embodiments herein.
Therefore, it is the object of the appended claims to cover all
such variations and modifications as come within the true spirit
and scope of the embodiments herein.
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